1. Field of the Invention
The present invention relates to a recovery device of a blasting medium and a method therefor, and particularly to a recovery device of a blasting medium of a sponge fragment of which porous elastic body contains an abrasive adhering thereto, and a method therefor.
2. Description of the Related Art
When recoating a coated wall surface, blasting operation is conducted as preparatory work to grind the coat layer off the wall thereby roughening the coating surface for substrate conditioning.
Such blasting operation has been conducted by a sand blasting method such as described in, for example, Japanese Patent Application Laid-Open No. 9-109029. A sand blasting method is a method for injecting sand (blasting material) from a nozzle with a high speed air causing it to collide against the coating surface to grind the coat layer off the coating surface with the impact force thereby roughening the surface.
The sand blasting method, however, had a problem in that since the blasting material is rebounded with strong force, there occurs scattering of dust particles. Further, there was a drawback that the operator who handles the nozzle must be heavily equipped for protecting himself or herself from the blasting material rebounded with strong force thus suffering poor workability. Furthermore, since the operator has a very poor visual field due to the scattered dust particles, it was difficult to perform the operation at a uniform quality.
To solve such problems, there is a known method, so called a sponge blasting method, which utilizes a blasting medium of a sponge fragment of which porous elastic body contains an abrasive adhering thereto.
According to this sponge blasting method, when the sponge blasting media, which has been injected from a nozzle with a high speed air, collides against the coating surface, the blasting media becomes flattened causing the mixed abrasive to collide directly against the coating surface at a high speed. This allows, as with the sand blasting method, the coat layer to be ground and removed. Further, since dust particles, which would otherwise float in the air, will be taken into the sponge fragment and fall as they are, the method offers an advantage of decreasing the scattering of dust particles. Furthermore, there is another advantage that since the sponge fragment absorbs repulsive force, the bouncing off is significantly reduced thereby circumventing the need of heavy equipment for the operator who handles the nozzle.
Further, Japanese Patent Application Laid-Open No. 2003-222475 discloses a classification method of copper slag used as the sand blasting material, to obtain the slag having a particle size of around 1500 to 3500 micrometers, which is useful as the sand blasting material, by sieving with a jumping screen.